118 research outputs found
Discovery of a Giant Radio Halo in a New Planck Galaxy Cluster PLCKG171.9-40.7
No full textWe report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from a NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, has an extent of approx.1 Mpc and a radio power of approx. 510(exp 24)W/Hz at 1.4 GHz. Its integrated radio spectrum has a slope of alpha approx. = 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMMNewton X-ray data shows that the cluster is hot (approx. 10 keV) and disturbed, consistent with X-ray selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck
Anticorrelation between X-ray luminosity and pulsed fraction in the Small Magellanic Cloud pulsar SXP 1323
No full textWe report the evidence for the anticorrelation between pulsed fraction (PF) and luminosity of the X-ray pulsar SXP 1323, found for the first time in a luminosity range 1035-1037 erg s-1 from observations spanning 15 yr. The phenomenon of a decrease in X-ray PF when the source flux increases has been observed in our pipeline analysis of other X-ray pulsars in the Small Magellanic Cloud. It is expected that the luminosity under a certain value decreases as the PF decreases due to the propeller effect. Above the propeller region, an anticorrelation between the PF and the flux might occur either as a result of an increase in the unpulsed component of the total emission or a decrease of the pulsed component. Additional modes of accretion may also be possible, such as spherical accretion and a change in emission geometry. At higher mass accretion rates, the accretion disc could also extend closer to the neutron star surface, where a reduced inner radius leads to hotter inner disc emission. These modes of plasma accretion may affect the change in the beam configuration to fan-beam dominant emission.</p
Discovery of a radio relic in the low mass, merging galaxy cluster PLCK G200.9−28.2
No full textRadio relics at the peripheries of galaxy clusters are tracers of the elusive cluster merger shocks. We report the discovery of a single radio relic in the galaxy cluster PLCK G200.9-28.2 (z = 0.22, M-500 = 2.7 +/- 0.2 x 10(14)M(circle dot)) using the Giant Metrewave Radio Telescope at 235 and 610 MHz and the Karl G. Jansky Very Large Array at 1500 MHz. The relic has a size of similar to 1 x 0.28 Mpc, an arc-like morphology and is located at 0.9 Mpc from the X-ray brightness peak in the cluster. The integrated spectral index of the relic is 1.21 +/- 0.15. The spectral index map between 235 and 610MHz shows steepening from the outer to the inner edge of the relic in line with the expectation from a cluster merger shock. Under the assumption of diffusive shock acceleration, the radio spectral index implies a Mach number of 3.3 +/- 1.8 for the shock. The analysis of archival XMM-Newton data shows that PLCK G200.9-28.2 consists of a northern brighter sub-cluster, and a southern sub-cluster in a state of merger. This cluster has the lowest mass amongst the clusters hosting single radio relics. The position of the Planck Sunyaev-Ze'ldovich effect in this cluster is offset by 700 kpc from the X-ray peak in the direction of the radio relic, suggests a physical origin for the offset. Such large offsets in low mass clusters can be a useful tool to select disturbed clusters and to study the state of merger
Characterizing the First Galaxy Clusters at the Epoch of their Formation with STAR-X
No full textThe next generation survey with the South Pole Telescope (SPT-3G) will discover all galaxy clusters with masses above 10^14 Msun. Due to the comparable angular resolution of these SZ observations and the size of these high redshift clusters, we require higher resolution observations across the electromagnetic spectrum to reveal their morphology and other detailed properties. At present, such information on the ICM is most accessible at X-ray energies. We have proposed a new MidEx-class X-ray observatory, the Survey and Time-domain Astrophysical Research eXplorer (STAR-X), capable of surveying 300 z>1.5 clusters and a thousand more at lower redshifts in its prime 2-year mission. With 5" angular resolution, over 2500 cm^2 of effective area, and soft X-ray sensitivity, STAR-X will be able to resolve the ~8" spatial structures that XMM-Newton cannot quite disentangle and gather photons >4x faster than Chandra. Its large 1 deg^2 FOV and low background will also allow the outskirts of many nearby clusters to be mapped out to the virial radius. I will discuss how this new mission will expand our current understanding of how galaxy clusters form and evolve over all of cosmic time
Do electrons ghost Ions after a merger? - a NuSTAR investigation of intracluster plasma in Abell 2146
No full textposterGalaxy clusters are the most massive gravitationally bound objects in the universe. Cluster mergers convert upwards of 1065 ergs of gravitational potential energy into the kinetic energy of the intracluster medium (ICM), the hot ionized plasma between galaxies in a cluster (Zuhone & Su 2022). Merger features in the ICM help constrain plasma physics parameters such as electron-ion thermal equilibration timescales (eiTETs) across shock fronts between equilibration in a matter of seconds (instant model) and equilibration over tens of millions of years (collisional model). This poster shares results of processing a ~260 kilo-second NuSTAR observation of the galaxy cluster merger Abell 2146 and report best fits of the post-shock temperatures and the eiTETs in the two ~10 keV shock fronts the cluster possesses. So far, constraints on eiTETs in cluster mergers have shown a mixed bag of results potentially due of Chandra X-ray telescope\u27s over-estimation of temperatures beyond its upper limit of 10 keV (Wallbank 2022). This makes using NuSTAR\u27s hard X-ray imaging capabilities on the Chandra - studied Abell 2146 an important calibration experiment. Abell 2146 Gravitational Potential energy Kinetic energy Thermal en-ergy Thermalization
The NuSTAR, XMM-Newton, and Suzaku view of A3395 at the intercluster filament interface
No full textGalaxy clusters are the largest virialized objects in the universe. Their
merger dynamics and their interactions with the cosmic filaments that connect
them are important for our understanding of the formation of large-scale
structure. In addition, cosmic filaments are thought to possess the missing
baryons in the universe. Studying the interaction of galaxy clusters and
filaments therefore has the potential to unveil the the origin of the baryons
and the physical processes that occur during merger stages of galaxy clusters.
In this paper, we study the connection between A3395 and the intercluster
filament with NuSTAR, XMM-Newton, and Suzaku data. Since the NuSTAR observation
is moderately contaminated by scattered light, we present a novel technique
developed for disentangling this background from the emission from the
intracluster medium. We find that the interface of the cluster and the
intercluster filament connecting A3395 and A3391 does not show any signs of
heated plasma, as was previously thought. This interface has low temperature,
high density, and low entropy, thus we suggest that the gas is cooling, being
enhanced by the turbulent or tidal 'weather' driven during the early stage of
the merger. Furthermore, our temperature results from the NuSTAR data are in
agreement with those from XMM-Newton, and from joint NuSTAR and XMM-Newton
analysis for a region with ~25% scattered light contamination within 1 sigma.
We show that the temperature constraint of the intracluster medium is valid
even when the data are contaminated up to ~25% for ~5 keV cluster emission.Comment: 22 pages, 13 figures, 7 tables. Accepted for publication by Ap
The Swift BAT Perspective on Non-Thermal Emission in HIFLUGCS Galaxy Clusters
No full textThe search for diffuse non-thermal, inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been underway for many years, with most detections being either of low significance or controversial. Until recently, comprehensive surveys of hard X-ray emission from clusters were not possible; instead, individually proposed-for. long observations would be collated from the archive. With the advent of the Swift BAT all sky survey, any c1u,;ter's emission above 14 keV can be probed with nearly uniform sensitivity. which is comparable to that of RXTE, Beppo-SAX, and Suzaku with the 58-month version of the survey. In this work. we search for non-thermal excess emission above the exponentially decreasing, high energy thermal emission in the flux-limited HIFLUGCS sample. The BAT emission from many of the detected clusters is marginally extended; we are able to extract the total flux for these clusters using fiducial models for their spatial extent. To account for thermal emission at BAT energies, XMM-Newton EPIC spectra are extracted from coincident spatial regions so that both the thermal and non-thermal spectral components can be determined simultaneou,;ly in joint fits. We find marginally significant IC components in 6 clusters, though after closer inspection and consideration of systematic errors we are unable to claim a clear detection in any of them. The spectra of all clusters are also summed to enhance a cumulative non-thermal signal not quite detectable in individual clusters. After constructing a model based on single temperatur
Review of \u3ci\u3eAmerican Farm Tools: From Hand-Power to Steam-Power\u3c/i\u3e By R. Douglas Hurt
No full textR. Douglas Hurt deals with the invention and development of American farm implements and machinery with a special emphasis on the nineteenth century. The material is organized around the functions of various agricultural machines used in the major grain-growing states. Ten chapters focus on the improvements made in plows, grain drills, corn planters, cultivators, reapers, binders, headers, corn binders, corn shellers, threshing machines, combined harvesters, mowing machines, hay stackers, feed mills, and steam traction engines.
The author decided to describe certain lines of farm equipment without trying to catalogue all agricultural tools, implements, and machines. Therefore the reader will not find descriptions of such items as cotton gins, saw mills, blacksmith tools, windmills, irrigation pumps, wagons, buggies, washing machines, and hardware materials. Also, during the period 1892 to 1914, no mention is made of the manufacture of the internal combustion engine and its uses in stationary gas engines, the early tractors, automobiles, trucks, and electric light plants.
The judicious use of 219 photographs and illustrations gives a visual presentation of the evolution of rural technology. The verbal descriptions of mechanical and technical matters can be readily understood by the general reader. The book includes a good bibliography and a helpful appendix to aid the reader in understanding the importance of metallurgy as an important factor in the manufacture of farm machinery. Better farm machinery had to wait until the making of steel had been perfected.
Some readers would welcome more analysis and interpretation of rural technology. For example, virtually all historians mention that our colonial forefathers used the wooden plow, the sickle, and the flail to grow crops, the same tools used thousands of years earlier in Biblical times. Why was this progress so slow? Why were no new machines invented in colonial America in the 170 years prior to the Revolutionary War? Why did it take two hundred years of experimentation before the first successful track-type Caterpillar engines were built in 1904? Combines were widely used in the Pacific Coast states in the 1880s, yet they were not adopted in the Midwest until the late 1920s, a lag of forty years. Perhaps historians should give more attention to the factors that deter progress and to the obstacles that prevent the adoption of new ideas, to try to explain the inability of people to adopt new methods.
Nevertheless, the narrative is informative and well written. American Farm Tools is a fine addition to the historical record
NuSTAR and XMM-Newton view of the interaction between the galaxy cluster A3395 and A3395/A3391 intercluster filament
No full textAccording to large scale structure (LSS) formation scenarios, Galaxy Clusters (GCs) are thought to have formed hierarchically via mergers of smaller scale structures. Thermodynamical properties of the X-ray emitting intracluster medium are sensitive probes of these dynamical activities. In this talk, I will present the joint NuSTAR and XMM-Newton analysis of the GC A3395 (z = 0.0498) at the site where the cluster and the filament connecting A3395 and A3391 meet in projection. Although XMM-Newton detects a hot-spot in this location, which may point to accreted structures and/or internal dynamics, we find that NuSTAR does not agree with this result (possibly) due to its insensitivity to spatially varying foreground absorption that XMM-Newton suffers from. The interaction of cosmic web filaments and GCs, as we explore in our joint analysis of A3395, can help improve our understanding of the formation and growth of LSS
Agri-food clusters: Does French policy match with real spatial dynamics?
No full textIn this paper, we attempt to ascertain to what extent the clusters identified in the agricultural and agri-food space rely on a spatial dynamic involving real agricultural and agri-food activities in the relevant geographic area. We use explanatory spatial data analysis (ESDA) to detect the spatial structure and dynamics of agri-food activities and to connect them to the competitiveness clusters’ locations. Results show that the six clusters specifically studied have different profiles because of their proximity to dynamic areas of agricultural and agri-food production and because of their collaborations with other clusters. Keywords: French Competitiveness Clusters, spatial analysis, inter cluster collaboration.
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